Power density

About: Power density is a research topic. Over the lifetime, 9534 publications have been published within this topic receiving 197264 citations. The topic is also known as: volumic power & volume power density.

Performance of a piezoelectric harvester in thickness-stretch mode of a plate

Abstract: We studied mechanical-to-electrical power conversion of a piezoelectric plate driven mechanically into thickness-stretch vibrations. We have derived an analytical solution from the three-dimensional equations of linear piezoelectricity that shows the role of each of the physical parameters in determining the performance of such a piezoelectric device, usually measured by the output power density, the power efficiency, or both. Numerical results are included for illustrating the dependence of the device performance upon these physical parameters.

Maximization of Spatial Charge Density: An Approach to Ultrahigh Energy Density of Capacitive Charge Storage

Abstract: Capacitive energy storage has advantages of high power density, long lifespan, and good safety, but is restricted by low energy density. Inspired by the charge storage mechanism of batteries, a spatial charge density (SCD) maximization strategy is developed to compensate this shortage by densely and neatly packing ionic charges in capacitive materials. A record high SCD (ca. 550 C cm-3 ) was achieved by balancing the valance and size of charge-carrier ions and matching the ion sizes with the pore structure of electrode materials, nearly five times higher than those of conventional ones (ca. 120 C cm-3 ). The maximization of SCD was confirmed by Monte Carlo calculations, molecular dynamics simulations, and in situ electrochemical Raman spectroscopy. A full-cell supercapacitor was further constructed; it delivers an ultrahigh energy density of 165 Wh L-1 at a power density of 150 WL-1 and retains 120 Wh L-1 even at 36 kW L-1 , opening a pathway towards high-energy-density capacitive energy storage.

High Capacity Thermoelectric Temperature Control Systems

Abstract: Recent advances in TE technology enable a new class of solid state cooling, heating, and temperature control systems. The new designs utilize advanced thermodynamic cycles [Bell, LE, 2002] to improve the Coefficient of Performance (COP) by about a factor of two, so that performance levels are comparable to those of two phase compressor based systems in certain important applications. Further improvement has resulted from optimized designs that employ TE components with increased power density [Diller, RW, et. al., 2002] and reduced temperature differentials at the TE/electrode interfaces in the heat transfer path. Together, these improvements enable new system configurations that in important applications are performance competitive with two phase systems for heating and cooling capacities of up to 3,500 watts. By utilizing high power design concepts and system level design optimization [Bell, LE, 2004], TE material costs per watt of thermal power output is reduced by about a factor of four. A system design is presented that is suitable for output thermal power ranging from 50 to 5,000 watts in either heating or cooling modes. The present design is compared with a similar design using conventional TE modules in terms of size, weight, efficiency, and power density. Experimental results are presented that demonstrate good correlation between measured values and the predicted COP performance enhancements and TE material usage reductions

Hyperthermia by magnetic induction: I. Physical characteristics of the technique

Abstract: Several electromagnetic techniques are currently used in hyperthermia therapy for cancer. This report discusses the magnetic induction technique, in which application of an alternating magnetic field to a conductor results in induction of eddy current flow and power deposition via ohmic losses. The power density in tissues depends upon the heterogeneous tissue conductivities and dielectric constants, magnetic field intensity and distribution, and eddy current radius. Using a newly developed magnetic field probe, the magnetic fields produced at 13.56 MHz by electrodes of a commercial magnetic induction device have been accurately mapped and used to calculate power densities in static phantoms. Calculated and observed temperature elevations in a cylindrically symmetric phantom agree well, confirming the simple formula in this case relating power density to magnetic field strength. The efficiencies of three commercially available electrodes have been accurately measured using calorimetric techniques and phantom loads modeling human anatomy and electrical conductivity. The effect of eccentric positioning of the load has been studied using magnetic field mapping techniques. Power densities in a very simplified model of human anatomy that retains cylindrical symmetry were calculated. Effects of inhomogeneities in conductivity have been investigated qualitatively using composite static phantoms modeling human cross-sectional anatomy and thermographic camera recordings of surface temperature distributions. The advantages and disadvantages of this heating technique are discussed from the point of view of the power density distributions in heterogeneous materials. Evaluation of power density distributions is essential for optimizing this heating technique using various electrode arrangements and/or load modifications, for providing part of the information needed for solution of the bioheat transfer equation in living subjects, and for predicting the ability of the technique to heat specific tumors.